This invention relates to a system for supply of seal gas to gas lubricated, non-contacting seals. More particularly, it relates to a system of conditioning elements for supply of conditioned gas to the seal chamber.
Various types of rotary devices involving pressurized gas within a housing employ gas lubricated, non-contacting seals between the rotating shaft and housing to contain the process gas within the housing. These include gas compressors, turbo-expanders, gas turbines, steam turbines, and the like, as well as pumps that have gaseous barrier fluid-type seals. U.S. Pat. No. 4,212,475 is exemplary of such gas lubricated, non-contacting seals.
The seals are disposed along the shaft and separate the pressurized process fluid chamber within the machine housing from the surrounding environment. Typically, the seal assembly is located in a seal chamber separated from the process fluid chamber by a labyrinth seal arrangement. Seal gas is supplied to the seal chamber to provide the fluid necessary for seal operation. Such gas may be from an external source, such as a nitrogen supply. Commonly though, process gas received from the equipment being sealed is the source of the seal gas. Appropriate lines and passages are provided which communicate the gas to the seal chamber through a seal gas supply system.
A system, contemplated for use in applications as described above, is shown in U.S. Pat. No. 6,345,954. That system provides a supply of process gas to the seal chamber from the discharge end of a gas compressor. This source of seal gas is not always at a pressure that exceeds the pressure of the process gas. To insure an adequate seal gas pressure, a booster compressor is employed to provide a pressure sufficient to supply seal gas for operation of the seal. Direct entry of process gas into the seal cavity, for example across the labyrinth seals, is avoided. Also, a filter of some type is disclosed which initially receives the gas supplied to the seal chamber.
The system described in U.S. Pat. No. 6,345,954 focuses on assurance of a seal gas pressure that precludes entry of process gas directly into the seal chamber. Though a filter is disclosed, no particular mention is made of gas treatment apart from pressurization. This approach does not address all needs associated with a suitable seal gas supply system. Particularly absent are arrangements for conditioning of the supplied seal gas to ensure maximum protection of the seal components and consistent non-contacting operation on a gaseous film. Such needs are most significant where the process gas is not of a quality or condition to support operation of the seal. The present invention addresses this deficiency.
Also, the system disclosed in U.S. Pat. No. 6,345,954 demands that the seal gas supply emanate from a single source, regardless of whether pressurized by the machine being sealed or by the booster compressor. Such an arrangement does not contemplate an alternate source of a gas supply for booster compressor operation.
In addition, operation of the system is dependent upon the sensing of pressure differential between the inlet and discharge of the machine being sealed. This approach does not provide the advantage attendant to more direct recognition of the need to amplify or augment the seal gas pressure level as is contemplated by the present invention.
The present invention is directed to a system for supply of conditioned seal gas to the seal chamber of a rotary machine employing gas lubricated, non-contacting seals. In a broadest form, it includes conditioning elements to remove particulate solid and liquid and volatile components from the gas which would be disruptive of seal operation or deleterious to seal durability as well as to heat the gas to a predetermined level, if necessary, to ensure a continuous supply of gaseous fluid for seal operation. The system may also include an element to amplify pressure of the seal gas. The amplification element is responsive to sensing of a condition of the gas to be supplied to the seal chamber to operate the pressure amplifier and ensure that an adequate supply of seal gas is available at the requisite pressure. The conditioning elements may be assembled onto a single skid.